Try Suitability patterns. I've used the horse blanket one; the hay bags pattern; the nose bag and the cantle bag. Oh, and the saddle cover and bit carrier. They were pretty easy to follow, although I've been sewing for 40+ years, so can't really say what they might be like for a beginner (sorry if you're not; kind of assumed that from your post).
The hardest part was trying to draw the horse blanket on the fabric. After making a couple, I laid down a ready-made blanket that I knew fit and traced that. Also, if you make the saddle carrier, the quilting step is a pain--lots of stuff to fit in the sewing maching.
That said, good luck. It's fun to do your own because you can use the color you want.
The trail is the thing....Louis L'Amour